The Circle Series, formerly known as the Circle Trilogy until the novel Green was released in September 2009, is a pentalogy of spiritually inspired novels by American author Ted Dekker, written mostly in 2004, about a man named Thomas Hunter who, after a head injury, wakes up in an alternate reality every time he goes to sleep. The stakes are raised when he realizes that a deadly virus is about to be unleashed in the world, and that the other earth is also being threatened with catastrophe. The pace quickens as links and parallels between the two worlds are revealed, and the clock begins to run down for both worlds.